Low-field magnetotransport in graphene cavity devices

Confinement and edge structures are known to play significant roles in electronic and transport properties of two-dimensional materials. Here, we report on low-temperature magnetotransport measurements of lithographically patterned graphene cavity nanodevices. It is found that the evolution of the low-field magnetoconductance characteristics with varying carrier density exhibits different behaviors in graphene cavity and bulk graphene devices. In the graphene cavity devices, we have observed that intravalley scattering becomes dominant as the Fermi level gets close to the Dirac point. We associate this enhanced intravalley scattering to the effect of charge inhomogeneities and edge disorder in the confined graphene nanostructures. We have also observed that the dephasing rate of carriers in the cavity devices follows a parabolic temperature dependence, indicating that the direct Coulomb interaction scattering mechanism governs the dephasing at low temperatures. Our results demonstrate the importance of confinement in carrier transport in graphene nanostructure devices.Comment: 13 pages, 5 figure

Differences in thermal-acoustic perception in various office behaviors

Thermal-acoustic interaction has vital research value in the development of soundscape prediction models. Previous studies on thermal-acoustic interaction have been focused mainly on perceptual changes. However, the differences in office behaviors warrant attention. We conducted an experimental study to explore the effects of various office behaviors (such as resting, reading, writing, and typing) on the thermal-acoustic interactive perception. The results showed that (at near thermal neutral temperature) (1) sound types affected thermal evaluation, acoustic evaluation, and overall evaluation. The sound of water significantly reduced the score for thermal sensation. (2) Behavior types affected thermal sensation, acoustic comfort, and overall comfort. Reading contributed to significantly lower scores than other behaviors for the three indicators. This indicated that when reading, people are more demanding of the environment. (3) The interaction of sound types and behavior types affected overall annoyance. Therefore, we recommend adjusting the office environment effectively and establishing more effective soundscape prediction models

On the effectiveness of facial expression recognition for evaluation of urban sound perception

Sound perception studies mostly depend on questionnaires with fixed indicators. Therefore, it is desirable to explore methods with dynamic outputs. The present study aims to explore the effects of sound perception in the urban environment on facial expressions using a software named FaceReader based on facial expression recognition (FER). The experiment involved three typical urban sound recordings, namely, traffic noise, natural sound, and community sound. A questionnaire on the evaluation of sound perception was also used, for comparison. The results show that, first, FER is an effective tool for sound perception research, since it is capable of detecting differences in participants' reactions to different sounds and how their facial expressions change over time in response to those sounds, with mean difference of valence between recordings from 0.019 to 0.059 (p < 0.05or p < 0.01). In a natural sound environment, for example, facial expression increased by 0.04 in the first 15 s and then went down steadily at 0.004 every 20 s. Second, the expression indices, namely, happy, sad, and surprised, change significantly under the effect of sound perception. In the traffic sound environment, for example, happy decreased by 0.012, sad increased by 0.032, and surprised decreased by 0.018. Furthermore, social characteristics such as distance from living place to natural environment (r = 0.313), inclination to communicate (r = 0.253), and preference for crowd (r = 0.296) have effects on facial expression. Finally, the comparison of FER and questionnaire survey results showed that in the traffic noise recording, valence in the first 20 s best represents acoustic comfort and eventfulness; for natural sound, valence in the first 40 s best represents pleasantness; and for community sound, valence in the first 20 s of the recording best represents acoustic comfort, subjective loudness, and calmness

Formation of Long Single Quantum Dots in High Quality InSb Nanowires Grown by Molecular Beam Epitaxy

We report on realization and transport spectroscopy study of single quantum dots (QDs) made from InSb nanowires grown by molecular beam epitaxy (MBE). The nanowires employed are 50-80 nm in diameter and the QDs are defined in the nanowires between the source and drain contacts on a Si/SiO$_2$ substrate. We show that highly tunable QD devices can be realized with the MBE-grown InSb nanowires and the gate-to-dot capacitance extracted in the many-electron regimes is scaled linearly with the longitudinal dot size, demonstrating that the devices are of single InSb nanowire QDs even with a longitudinal size of ~700 nm. In the few-electron regime, the quantum levels in the QDs are resolved and the Land\'e g-factors extracted for the quantum levels from the magnetotransport measurements are found to be strongly level-dependent and fluctuated in a range of 18-48. A spin-orbit coupling strength is extracted from the magnetic field evolutions of a ground state and its neighboring excited state in an InSb nanowire QD and is on the order of ~300 $\mu$eV. Our results establish that the MBE-grown InSb nanowires are of high crystal quality and are promising for the use in constructing novel quantum devices, such as entangled spin qubits, one-dimensional Wigner crystals and topological quantum computing devices.Comment: 19 pages, 5 figure

Effects of sound environment on the sleep of college students in China

Chinese college students reside primarily in four-person bedrooms and even six-person bedrooms, where the sound from roommates may affect their sleep. Therefore, the purpose of the present study is to investigate the effects of different sound sources and sound levels on sleep for college students in China. Based on sleep quality measurements, acoustic environment measurements, and a questionnaire survey with 90 participants in a typical residence hall in Harbin city, China, the results are as following: First, 68.89% of college students experienced sleep deprivation, and indoor noise was the most influential environmental factor among 15 disruptors that disturbed 50% of college students. Second, the number of occupants per room was a significant factor affecting the background sound level of sleep, which was highest when the number of occupants was two, and lowest when the number was five. Third, deep sleep time and rapid eye movements (REM) sleep time decreased 1.7 min and 1.4 min per 1 dBA (decibel with A-weight), with R2 = 0.352 and 0.332, respectively (p < .001). In terms of the effect of sound sources on sleep, sleep was mostly disturbed by roommate conversation (77.42%), and noise caused by roommate sleep-related activities was the most common source of activities (67.74%). The present study can provide guidelines to help enhance the sleep quality of Chinese college students through improvements in the sound environment

Two-dimensional structures of ferroelectric domain inversion in LiNbO3 by direct electron beam lithography

We report on the fabrication of domain-reversed structures in LiNbO3 by means of direct electron beam lithography at room temperature without any static bias. The LiNbO3 crystals were chemically etched after the exposure of electron beam and then, the patterns of domain inversion were characterized by atomic force microscopy (AFM). In our experiment, an interesting phenomenon occurred when the electron beam wrote a one-dimensional (1-D) grating on the negative c-face: a two-dimensional (2-D) dotted array was observed on the positive c- face, which is significant for its potential to produce 2-D and three-dimensional photonic crystals. Furthermore, we also obtained 2-D ferroelectric domain inversion in the whole LiNbO3 crystal by writing the 2-D square pattern on the negative c-face. Such a structure may be utilized to fabricate 2-D nonlinear photonic crystal. AFM demonstrates that a 2-D domain-reversed structure has been achieved not only on the negative c-face of the crystal, but also across the whole thickness of the crystal.Comment: 17 pages, 4 figure